Glossary

HC

Hazard characterisations (HCs) is a generic term for any reference value for a substances at a chosen biological target level (external or internal) beyond which exposure is associated with potential adverse health effects. Hazard characterisations can be specified as external values (e.g., a human based guidance value, such as an ADI or ARfD) or are based on a point of departure (POD), such as BMDs from dose-response models or externally specified points of departure (NOAEL, LOAEL, MDS). The computation may involve assessment factors, e.g., for inter-species conversion, intra-species variation or additional sources of uncertainty. The calculation may also use kinetic models or absorption factors to convert external doses to internal doses or vice versa.

HI

The hazard index (HI) is the sum of all hazard quotiens (HQ) of the substances that are associated with the same potential adverse health effect.

HQ

The hazard quotient (HQ) is the ratio of the exposure to a substance and the reference level at which no adverse effects are expected (i.e., exposure divided by the reference level). A HQ smaller than 1 is associated with no expected adverse health effect and a HQ larger than 1 is associated with possible adverse health effects. The HQ is closely related to the MOE, which can be seen as the inverse metric.

MOE

The margin of exposure (MOE) is the ratio between the reference level at which no adverse effects are expected to the exposure to a substance (i.e., reference level divided by exposure). Commonly, the reference level is assumed to be a point of departure (POD) based on animal studies that does not incorporate all factors to translate to a human reference value. A MOE is therefore typically compared to a uncertainty/safety factor (UF) composed of the product of the uncertainty factors. An MOE is smaller than the UF is associated with risk. A MOE larger than the UF is associated with no expected adverse health effects.

POCE

The probability of critical effect (PoCE) is the proportion of the HI distribution above the threshold (or of the generalised MOE below the threshold) is the probability of critical exposure (PoCE) in the particular (sub)population. The threshold value can be 1 if all assessment factors have already been accounted for in the calculation of HI or MOE.

POD

A point of departure (POD) is defined as a point on a toxicological dose-response curve obtained from a dose dose-response experiment in the region at which the curve transitions from no effects to effects. It is used as the base value for deriving toxicological reference values, or hazard characterisations. Common PODs are the no-observed adverse effect level (NOAEL) and benchmark dose (BMD).